The technique of using a scanning apparatus to scan documents is well-known in the art. Regardless of transparent documents or opaque documents, a light source has to be provided to emit light, which projects to the document and enters into an optical module in the scanning apparatus to perform image scanning. For scanning opaque documents, the light emitted by the light source projects to the document, which reflects the light to the optical module to perform image scanning of the opaque document. For scanning transparent documents, the light emitted from the light source penetrates the document to reach the optical module so as to perform image scanning of the transparent document. Hence, the the conventional dual-purpose scanners for transparent documents and reflective documents mostly have the reflective light source installed in the scanner host, and have the transparent light source installed in the lid of the scanner, but such a design has two independent light sources, and takes a great deal of space. Many elements are needed and the cost is higher.
To remedy the aforesaid problems, scanners that can scan transparent documents and reflective documents through using one light source have been developed. For instance, R.O.C. patent publication No. I220095 discloses a technique that has a lid including a reflective mirror and a light guide plate. Light emitted form a light source passes through two sides of the transparent document and is reflected by the reflective mirror to the light guide plate. The light guide plate directs the light to pass through the transparent document to perform scanning. Such a design can reduce the number of elements and save costs partially. However, it still requires a lot of space.